Typical prior art film cassettes comprise a cover which is hingedly mounted to a base such that when the cover is closed on the base, there is provided a light-tight space therebetween for receiving photosensitive x-ray film. Secured to the inside surface of the cover is a foam pad having an intensifying screen secured to its outer surface. When the cover is in the closed position, the foam pad and intensifying screen pushes the x-ray film firmly against the base of the cassette. Appropriate latching means are provided for latching and unlatching the cover with respect to the base. With cassettes that are designed for use in mammography it is important that the film be placed closely adjacent the edge of the cassette that is placed against the patient and that the best possible image be obtained along the edge as well as in the central area of the film.
A problem experienced with prior art cassettes is that there is a lack of good film contact between the intensifying screen and the adjacent a-ray film, especially along the edges of the film. Foam pads used in prior art cassettes typically comprise a single layer of a resilient material. The foam pad generally provides relatively little force at the edge areas of the film as opposed to the areas distal from the edges. Additionally, the latching mechanism is often provided adjacent the edge of the cassette to be placed against the patient. The foam pad and attached intensifying screen is simply placed directly over the latching mechanism which further contributes to inconsistent uniform contact between the intensifying screen and film in this area.
Applicant has invented an improved cassette which minimizes or eliminates many of the problems of the prior art and also provides a cassette that is easy and economical to manufacture.